docs: def efflam(self,binned=True):
          """Calculate :ref:`effective wavelength <pysynphot-formula-efflam>`
          of the observation.
          Calculation is done in the flux unit of ``flam``.
  
          .. note::
  
              Similar to IRAF STSDAS SYNPHOT ``efflphot`` task.
  
          Parameters
          ----------
          binned : bool
              Use binned dataset for calculations. Otherwise, use native dataset.
  
          Returns
          -------
          ans : float
              Effective wavelength.
  
          """
          myfluxunits=self.fluxunits.name
          self.convert('flam')
          if binned:
              wave=self.binwave
              flux=self.binflux
          else:
              wave=self.wave
              flux=self.flux
  
          num = self.trapezoidIntegration(wave,flux*wave*wave)
          den = self.trapezoidIntegration(wave,flux*wave)
          self.convert(myfluxunits)
  
          if num == 0.0 or den == 0.0:
              return 0.0
  
          return num/den